It would be much more easier to have one but I don't think it's really necessary. The cap isn't torqued to the point where it is difficult to turn by hand (18ft/lbs or 25NM). But if you really want to get one, ECSTuning has one for about $25 (before shipping).

Are you able to torque the cap to spec without the tool flexing or damaging the cap..? I was going to get it, but my experience with the steel ones isn't as good as the cast Aluminum ones. The Al ones are a little beefier and don't flex at all, but the steel ones can slightly flex. If that happens, the torque is off and the flexing ends up damaging the plastic cap.